1. Technical Field
The disclosure relates to a technique for acquiring depth image. Particularly, the disclosure relates to a zoom type depth image acquiring device, a calibrating method and a measuring method thereof.
2. Related Art
Today's image sensing technology becomes more mature. Besides obtaining two-dimensional (2D) images, how to effectively, opportunely and stably obtain 3D (i.e. depth) information of an object to be tested becomes an important issue in depth image sensing technology. Since the depth image sensing technology can estimate a distance between an image acquiring device and the object to be tested, integral 3D space information can be provided, which can be used in interfaces of an interactive browsing device and somatosensory games, and is also gradually applied in security video surveillance, robot vision, and medical imaging. A somatosensory game device, Kinect, is published by Microsoft uses the depth image sensing technology as a core element, such that human motions can serve as an media control interface of the game, which causes sales booming of the device, and more manufacturers pay attentions to the depth image sensing technology and applications thereof.
An image acquiring device (for example, a depth camera) using the depth image sensing technology is generally implemented by using prime lens since related image acquiring parameters can be easily calibrated in advance. However, range of viewing angle (which is also referred to as a sensing range) and image resolution of depth camera adopting prime lens are also fixed. Therefore, if the object to be tested is too large and exceeds the viewing angle range, a position of the fixed focal length depth cameral is required to be manually adjusted. If the size of the object to be adjusted is too small to cause blurriness of the acquired image (i.e. the image resolution is too small), depth sensing performed through the acquired image could not be implemented. However, if zoom lens are used in the implementation of the depth camera, the issue of setting and adjusting focal lengths of the zoom lens is a problem to be solved in the calibration of the depth camera in the recent depth image sensing technology.